Telephone-exchange system.



A. B. SPERRY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 6,1916.

' Patented June 26, 1917.

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APPLICATION FILED NOV. 6,1916.

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A. B. SPERRY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED NOV. 6. l9l6.

Patented June 26, 1917.

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ARTHUR B. BPEBBY, 01 NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, 0! NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented June 26, 1917.

Application nled November 6, 1918. Serial No. 129,789.

To all whom it may concern:

Be it known that I, ARTHUR B. SPERRY, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machine switching, and particularly to that type of system wherein a connection leads through a number of ofiices which are interconnected by two-wire trunks, and therein a set of repeating relays is located before the first selector to repeat impulses from the sender to the automatic switches.

Its object is to provide a system of this character wherein the impulses are repeated over a local grounded circuit from the repeating relays to the switches in the originating oflice, and to provide for automatically changing the control circuit from a grounded circuit to a metallic circuit when a trunk is selected leading to a distant ofiice.

In accordance with this invention, an elec tromagnetic switch is associated with the re peating relay set to control the character of the impulse circuit, this switch being in turn controlled by a device associated with one of the switches at the originating office in such a way that, when such switch is set upon a trunk level leading to a distant ofiice, the electromagnetic switch operates to change the impulse circuit from a grounded circuit to a metallic circuit. Preferably, the electromagnetic switch consists of a pair of switching relays which remain inert as long as a connection is being set up over a local grounded circuit, including switches at the originating oflice, the control circuit including the armature and back contact of one of such relays. When, however, a trunk group is selected leading to a distant office, these relays are operated, and include a marginal relay at the originating office in circuit with the repeating relay at the distant oflice, this circuit being completed at an armature and front contact of the stepping relay at the ofiice and are controlled at an armature and front contact of the stepping relay at the originating ofiice.

Referring to the drawings, Figures 1, 2 and 3, taken together, illustrate the circuit arrangement of this invention.

The invention will be best understood by describing in detail the operations involved in setting up a connection.

Upon the removal of the calling subscribers receiver at substation A, the line relay LR is energized over the line circuit, and in attracting its inner armature, grounds the multiple 100 of the calling line in the finder, and in attracting its outer armature, grounds commutator segment 101 of the group to which substation A belongs. The attraction of the outer armature of relay LR also energizes relay 102, common to the group of lines to which substation A belongs, over the following circuit: free pole of battery, relay 102 outer armature and front contact of relay R, conductor 103, left armature and back contact of--slow relay 104 to ground. Relay 102, in attracting its left armature, locks itself u and closes a circuit for relay LR, indepen ently of the initial energizing circuit leading to the calling substation, whereby, even thou h the receiver is replaced upon the hoo the finder will complete its operation. The attraction of the right armature of relay 102 closes the following circuit for primary magnet PM to drive the finder in a primary direction: free pole of battery, magnet PM, armature and ack contact of said magnet, side-switch arm 105 and its first contact, armature and back contact of the escape magnet 106 of the contact of slow 'relay 107 relay 104 to ground, at the right armature and front contact of relay 102. Primary magnet PM steps around the brush shaft 108 until the commutator brush 109 thereon reaches the grounded segment 101, whereupon the following circuit is. closed to energize the escape magnet to release the side switch into position 2: free pole of battery, magnet PM, arm 110, escape magnet 106, conductor 111, arm 112 and its first contact, conductor 113, commutator brush 109, commutator segment 101 to ground at the left armature and front contact of relay 102. The primary magnet locks u in series with the escape magnet when this circuit is closed thus positively positioning the brush shaf As the side-switch arm 112 leaves its first contact, the escape magnet denergizes, and in position 2the following circuit is closed for the secondary magnet SM to step the brushes 114, 115, 116 over the multiples 117 100 and 118 containing those of the calling line: free pole of battery, magnet SM and its armature and back contact, arm 105 and its second contact, armature and back contact of magnet 106, armature and back contact of magnet RM, left armature and back con-' tact of relay 107, conductor 138, relay 104 to ground at the right armature and front contact of relay 102. During this movement the right winding of test relay TR is in panallel with the secondary magnet SM, and these magnets energize together. At the end of the stroke of the armature of magnet SM, the test brush 116 of the line finder is in engagement with a multiple 118. If this multiple is grounded, as would be the case if the line to which it belongs were engaged in conversation, the rela TR would remain energized by its left winding and side-switch arm 112, and in maintaining its armature attracted, would prevent the escape ma at from energizing over a circuit inclu ing brush 115 and multiple 100. However, multiple 118 of the callin line is not grounded, and, consequently, w en the brushes 114,

' 115, 116 engage the multiples 117, 100 and 118 thereof, the following circuit is closed toenergize the escapement magnet 106 to release the side switch into position 3: free pole of battery, magnet SM, arm 110 and its second contact, magnet 106, armature and back contact of relay TR, arm 119, brush 115, multiple 100, inner armature and front contact of relay LR to ground at the left armature and front contact of relay 102. Magnets SM and 106 are locked in this circuit until the side-switch arm 119 passes off its second contact. In position 3 arm 112 closes the circuit of the cut-off relay CO, and grounds multiple 118 of the calling line to cause the same to test bu to other finders and to other connectors. e relay CO, in attracting its armatures, deenergizes the reof the repeating relay set: ree pole o battery, left winding of relay 121, arm 119 and its third contact, brush 115, multiple 100, through the telephonic apparatus at substa tion multiple 11.7, brush 114, arm 120, right winding of relay 121' to ground. Relay 121, in attracting its armature, energizes a slow relay 122, which, in attracting its right armature, removes ground from the conductor 123 leading to the'finder release magnet RM, to prevent premature release. Relay 104, being slow to release its armatures, is maintamed energized continuously during the setting of the finder switch, and does not retract its armatures completely until after the relay 122 has become energized. Thus the ground on the back contact of the relay 122 is not transmitted to the release magnet RM. The attraction of the right armature of relay 12 closes the following circuit for releaserelay RR', (Fig. 2) of the first selector: grounded right armature and front contact of relay 122, right armature and back contact of relay 107, contact 180, spring 170 of rela 134, conductors 132, 213, armature and bac contact of magnet R'M relay RR to free pole of battery. Relay R'R connects prlmary magnet PM' of the first selector to the upper talking conductor 200 and the 240 in series with the marginal release magnet RM to the lower talking conductor 202.

The calling party now'o'perates his sender S to transmit the first digit of the wanted number. This sender interrupts the line circuit in the well-known manner, and each time the relay 121 denergizes, an impulse is sent over the following path to the primary magnet PM of the first selector:

- ground, armature and back contact of relay conductors 126, 130 to prevent the discharge thereof from interfering with the character of the impulses. The attraction of the lower armature of relay 127 energizes the escapement magnet 240 of the first selector over the following circuit: ground, lower armature and front contact of relay 127, conductors 130, 202, arm 203 and its first conescape magnet.

tact, escape magnet 240, right armature and front contact of relay RR', release magnet RM, free pole of battery. The escape magnet 240 energizes when this circuit is closed, but the release magnet R'M' 1s marg1nal and does not. Upon the restoration of the sender S, the relay 121 (Fig. 1) remains energized, and after a short interval the slow relay 127 retracts its armatures, the retraction of the lower armature breaking the circuit of the escape magnet 240 of the first selector, which thereupon passes the side switch into the second position. In position 2 arm 204 completes the circuit of the secondary magnet S'M to drive the brushes 205, 206, 207 over the multiples 208, 209, 210 of the selected group of trunks.

When the first-selector side switch reaches position 2, the escape magnet 240 is again energized over sideswltch arm 211 and secondary off-normal contact S'O'N'. This contact opens on the first secondary step and the escape magnet is dependent for its main tained energization upon the grounds on the busy test multiples 210, as Wlll hereinafter appear. When the first ungrounded multiple 210 is reached, escape ma et 240 becomes deenergized, releasing t e slde switch into position 3. Arm 204, in moving off its second contact, opens the stepping circuit, thus stopping the selector upon the seized trunk. Arm 211 extends the grounded test conductor 213 to the test multi les 210 of the seized trunk which is amume to be a two-wire trunk leading to a distant ofiice.-

When a group of trunks is selected leading to a distant ofiice, a commutator brush 216 on the brush shaft 226 of the first selector grounds a conductor 227 to whlch 1s connected a pair of switching relays 172, 171.

This brush is grounded by arm 229 in position 2 of the first selector side switch. The energization of these relays results in changing over the sending c1rcu1t from a local grounded sending circuit to a metallic inter oflice sending circuit, as Wlll presently a pear. Relay 172 locks itself and relay 1 1 to ground at the right armature and front contact of relay 122, independently of the ground on the commutator brush 216, which ground is removed upon the first secondary step of the first selector brush shaft 226.

When the arms 201, 203 of the first Se lector side switch reach their third contacts, the following circuit is closed to ener 'ze the repeating relay 217 at the distant 0 cc: free pole of battery, left wlnding of relay 133, (Fig. 1) lower armature and back contact of relay 127 conductor 130, conductor 202, arm 203 and its third contact, brush 206, multiple 209, conductor 217, lower lefthand winding of repeating coil RC, both windings of relay 217, upper left-hand winding of repeating coil RC, conductor 218, multiple 208, brush 205, arm 201, conductor 200, conductor 126, upper armature and back contact of relay 127, right winding of relay 133, left armature and front contact of switchin relay 172 to ground at the armature an front contact of relay 121. The

relay 133 is marginal and does not become energized when this circuit isclosed, due to ing its right armature, connects the back contact of stepping relay 217 to the upper talking conductor 221 which leads to the primary stepping magnet P'"M of said selector.

The calling party now operates his sender to transmit the next diglt of the wanted number. Due to the energized condition of the relay 172, the relay 121, in operating in response to the sender, interrupts the metallic circuit traced leading to the distant oflice and including the repeating relay 217. 'Relay 217 denergizes upon each retraction of the armature of relay 121, and transmits an impulse to the primary ma et P M over the following circuit: groun armature and back contact of relay 217, armature and front contact of slow relay 219, conductor 222, left armature and back contact of relay 223, conductors 224, 221, 300, arm 301 and its first contact, magnet PM to free pole of battery. The magnet PM ste s the brushes 302, 303, 304 in a primary irection in operative relation to the desired group of trunk terminals 305, 306, 307. At the first retraction of the armature of relay 217, slow relay 231 is energized in parallel with PM, and in attracting its armatures, disconnects repeating coil RC from conductors 221, 232 and grounds conductor 232 to energize escape magnet 308. Relay 231, being slow, remains energized while relay 217 is operating. Upon the restoration of the sender and the consequent maintained energization of relay 121, relay 217 remains-" sition 3, in which position arm 304 grounds the test multiples 307 to cause the seized trunk to test busy to other incoming seleetors and energizes relay RR" which interposes a break in the circuit of release magnet RM of the connector C. 1

The calling subscriber now operates hlS sender to. transmit the tens digit of the called number, and'the relay 217 is a ain intermittently 0 erated, as described. ach retraction of t e armature of this relay transmits an impulse to the primary magnet PM of the connector over the following circuit: ground, armature and back contact of relay 217, armature and front contact of relay 219, conductors 222, 224, 221, 300, arm 301 and its third contact, brush 302, multiple 305,'conductors 314, 315, arnj 317 and first contact of the connector side switch, left armature and back contact of busy relay BR, conductor 316, arm 318, magnet P M free pole of battery. In parallel with the circuit just traced, slow relay 319 is energized and remains energized during the transmission of impulses. This relay, in energizing, closes the following circuit for the escape magnet 320 of the connector: free pole of battery, escape magnet 320, armature and'back contact of ringing cutofi' relay RCO, arm 321, spring 322 of relay 319, armature of said relay, to ground. When the sender restores and maintains relay 121 (Fig. 1) energizes, relay 217 (Fig. 2) remains energized, and after an interval, slow relay 319 retracts its armature. This relay in retracting its armature opens the circuit of the escape magnet 320, and the escape magnet deenergizes, passing the side switch into position 2. In position 2 the arm 318 substitutes secondary magnet SM for the primary magnet PM in the stepping circuit. calling party 0 rates his sender to transmit the units digit of the wanted number, and causes the intermittent operation of. relay 217, an impulse is sent upon each retraction of the armature of such relay over the circuit previously traced to the side switch arm 318, from whence it passes to the secondary magnet SM. The slow relay 319 is also energized, as before, and energizes the escape magnet 320. When the sender restores and maintains the relay 121 energized, the relay 217 remains energized,

and after an interval, slow relay 319 retracts its armature, again deenergizing the escape magnet 320 which passes the side switch into position 3. In position .3, assuming the called line to be idle, ringing current is applied thereto. In this position arm 323 applies ground to test multiples 328 of the called line to cause the same to test busy to other connectors, and operates the cutofi' relay of such line to remove the control of the line relay of the selected line from the called party. In position 3 the slow relay 319 is again energized over arms 318 and 331. This relay, in attracting its Consequently when the armature, again energizes the escape magnet, which in attracting its armature, ap-

331 to ground.

When the called part removes his receiver, the ringing cuto rela RCO energizes, opening the circuit of escapement magnet 320, which in denergizing, passes the side switch into position 4. Relay 319, however, being slow, holds its armature attracted after the side-switch arm 321 reaches its fourth contact which results in an impulse being transmitted over the following circuit to operate the calling supervisory relay 233: grounded armature of relay 319, spring 322, arm 321 and its fourth contact, conductor 336, terminal 306, brush 303, arm 337 and its third contact, conductor 232, left armature and back contact of rela 231, lower ri ht winding of repeating coll RC, left win ing of relay 233, free pole of battery. Rela 233, in attracting its armature, short-circuits the h' h-resistance right winding of relay 217. he resultant increase in current causes the marginal relay 133 (Fig.

1) to energize. This relay, in attracting its armature, energizes the slow 'relay 134, which, at its outer armature and spring 170, applies ground to the test conductor 132 to hold up the release relay R'R' independently of the ground applied thereto at the right armature and front contact of relay 122.

This relay also energizes a slow rela 107, the function of which will be describe Relay 233, in attracting its right armature, energizes relays 223 and 234. Relay 234, in attracting its right armature, provides a substitute ground or test conductor 220, independently of that applied at the left armature and front contact of relay 219.- In attracting its left armature, relay 234 connects ground to the right winding of relay 233, whereupon this relay is maintained energized over the called line circuit.

Talking current is fed to the callin party over the windings of relay 121. T e condensers 128, 129 inductively connect the calling end of the circuit with the middle section, and the repeating coil RC inductively mature and back contact of relay 122 to ground. The retraction of----the armature of relay 121 opens the circuit leadin to the distant ofiice, thus deenergizing re ays 133 and217. Relay 133 in retracting its armature opens the circuit of relay 1341, which, in retracting its outer armature, removes ground from the test wire 132, 213, from which release rela RR of the firstselector is branched off. his relay in retracting its armature, closes the circuit of release magnet lt'M', which thereupon withdraws the holding pawls from the brush shaft, and when such shaft reaches its normal position, the opening of contacts PON causes the deiinergization of this magnet. The release magnet restores the side-switch arms in the well-known manner.

Relay 217, in retracting its armature, deenergizes relays 233 and 219. The retraction of the left armature of relay 219 removes ground from test conductor 220 leading to the incomin selector and connector, whereupon the re ease relays B B and BR deenergize. Relay R R in retracting its armature, energizes the release magnetItM of the incoming selector over a circuit including primary off -normal contact PO N which opens when the selectorbrush shaft reaches its normal position, thus deenerglzing the release magnet. Release relay RPR of the connector, in denergizing, energ zes release magnet RM over a circuit includ ng primary off-normal contact P O N which opens when the connector brush shaft reaches its normal position, thus deenergizing the release magnet. The release magnet, in attracting its armature, grounds test multiple 307 to prevent the connector from being seized before the brush shaft thereof is entirely restored. The release magnets R M and 13 M restore the side switches upon their energization in the well-known manner.

The function of the slow relay 107 (Fig.

1) will now be explained. While the finder is operating, the group relay 102 interposes a break in the in-starter Wire 135 to prevent interference, and when the finder makes connection with the calling line A and operates the cutoff relay, the resultant de'energization of the relay 102 restablishes the continuity of the in-starter wire. A call then coming in from another group would ass over the following circuit to the next idle finder: in-starter wire 135, right armature and back contact of relay 102, slow relay 104, armature and back contact of relay 107, armature and back contact of magnet RM, armature and back contact of magnet 106, side-switch arm 105 and its third contact, out-starter Wire 136 to the primary stepping magnet of the next idle finder. The slow relay 104, in attracting its left armature, removes the control of the group relay 102 from the line relays of the group to which substation A belongs. The relay 107, while included in this circuit, does not energize, due to the presence of resistance 137. When the called party at substation B responds and ap lies ound to relay 107, in parallel with t e resistance 137, relay. 107 energizes and connects the in-starter wire 135 to the out-starter wire 136 independently of the side-switch arm 105. If the called party replaces his receiver when the in-starter wire 135 is grounded, by reason of, an incoming call from another group, and the calling party then replaces his receiver, relay 107, although its original energizing circuit is opened by the retraction of the armature of relay 134, does not become deenergized, since the circuit characteristics are such that the relay 107, while not energizing in series with the resistance 137, will hold up through this resistance. Consequently, the replacement of the receiver by the calling party at substation A, although causing the release of the finder and the restoration of the side-switch arm 105, does not interfere with the starting circuit to the finder beyond, since the relay 107 maintains its armature attracted to provide a circuit in substitution for that leading through the arm 105. When the ground is removed from the in-starter Wire 135, due to the finder having found. the line initiating the call, relay 107 becomes denergized and reconnects conductor 138 to the side-switch arm 105.

If the selected line had been busy either as a called or as a calling line, the test multiples 328 thereof would have been grounded either over the side-switch arm 112 of the finder (Fig. 1), or over the side-switch arm 323 of the connector (Fig. 3). When the connector test brush 335 is set upon such grounded multiple. 328, a circuit is closed for a busy relay BB, in series with the escape magnet 320, this circuit for the escape magnet being closed before the original energizing circuit for the same is opened as the armature of slow relay 319 moves out of engagementwith spring 322 of such relay, and is as follows: free pole of battery, escape magnet 320, armature and back contact of relay RCO, arm 321 and its second contact, make-before-break contact 322, relay BR, contact 338 thereof, arm 323 and its second contact, brush 335 to grounded multiple 328. The relay BR, in attracting its right armature, locks itself to ground over arm 331, independently of the ground on the multiple 328, and in attracting its left armature, applies a busy signal to the calling line from a busy tone apparatus 339.

\Vhen the calling party replaces his. receiver, the relay 121 becomes denergized,

whereupon the release of the switches and the restoration of all the apparatus to its normal condition takes place as described.

Considering now the case of a local call, that is to say, a call for a party whose l ne terminates in the same oflice as the calling party, a connection for such would lead over a number of selectors such as F S, by means of which a connector similar to C, is selected and set on the Wanted line. When the called party answers the connector side swltch passes to the fourth position, as described. The arm 321 reaches its fourth contact before the armature of slow relay 319 is retracted. This results in an impulse being transmitted over the lower talking conductor to the relay 133, as before, whereupon this relay attracts its armature and energizes slow relay 134. Relay 134, in attracting its inner armature, connects ground to the right winding of relay 133. Relay 133 is now maintained energized over a circuit including the called substation B and maintains relay 134 energized as described.

The outer armature of relay 13-1 in engaging spring 170, connects ground to test conductor 132, and removes the ground ap' plied to this conductor at the right armature and front contact of relay 122. Control of the release of all of the switches except the finder is thus transferred to the called party, upon the response of such party. Upon the termination of the conversation and the replacement of the receiver on the switchhook by the calling party, the relay 121 becomes decnergized, opening the circuit of relay 122, which in retracting its ri ht armature, energizes the release magnet M of the finder, as hereinbefore described. \Vhen the called party replaces his receiver, the relay 133, which in the case of a local call is in circuit with the called line, becomes denergized, and in retracting its armature, opens the circuit of slow relay 134. This relay in retracting its outer armature, removes ground from conductor 132, from which the release relays RR of the selectors and connector are branched off. These relays, in retracting their armatures, release their respective switches.

\Vhat is claimed is:

1. In a telephone exchange system, the combination with telephone lines. senders associated therewith. trunk lines including automatic switches adapted to interconnect said lines, driving magnets for said switches, a local grounded control circuit for said magnets, a set of repeating relays normally controlling said circuit and operated by said senders. a group of two-wire trunks connected to one of said switches. other automatic switches in which said trunks terminate, driving magnets therefor, a metallic control circuit including one of said twowire trunks and contacts of said repeating relays, and means for rendering inoperative said grounded control circuit and for rendering operative said metallic control circuit when said trunk group is selected.

2. In a telephone exchange system, the combination with telephone lines, senders associated therewith, trunk lines including automatic selector switches adapted to interconnect said lines, stepping magnets for said switches, a local grounded stepping circuit for said magnets, a set of repeating relays normally controlling said circuit and operated by said sender, a group of two-wire trunks connected to one of said switches, an oflice wherein said trunks terminate in automatic selector switches, stepping magnets for said switches, stepping relays for said switches, a circuit including one of said twowire trunks, the associated relay and contacts of said repeating relays, an electroresponsive device associated with said repeating relays adapted to render said grounded stepping circuit inoperative and to render said metallic stepping circuit operative, and a circuit for operating said device closed when said trunk group 15 selected.

3. In a telephone exchange system, the combination with telephone lines, senders associated therewith, automatic switches adapted to interconnect said lines, driving magnet-s therefor, a local grounded control circuit for said magnets, a set of repeating relays normally controlling said circuit and operated by said senders, a group of twowire trun s connected to one of said switches, other automatic switches in which said trunks terminate, driving magnets therefor, control relays for said magnets at said switches, a metallic control circuit including one of said trunks, the associated control. relay and contacts of said repeating relays, .an electromagnetic switching device associated with said repeating relays adapted to render inoperative said grounded control circuit and to render operative said metallic control circuit, and means associated with the selector containing said trunk group and adapted when said group is selected to operate said switching device.

4. In a telephone exchange system, the combination with telephone lines, senders associated therewith, automatic switches adapted to interconnect said lines. stepping magnets therefor, a local grounded stepping circuit for said magnets, a set of repeating relays normally controlling said circuit and operated by said sender, a group of twowire trunks connected to one of said switches, an oflice wherein said trunks terminate in automatic switches, stepping mag nets for said switches, stepping relays for said switches, a circuit including one of said two-wire trunks, the associated relay and adapted when said group is selected to operate sairl relays.

In witness whereof. I hereunto subscribe 10 my name this 2nd day of November, A. D. 1916.

ARTHUR B. SPERRY. 

